LONDON, July 19 (Reuters) - A rally in European stocks fizzled out on Thursday as poor results drove down advertising agency Publicis and a slide in metals prices dragged on the market.

As the earnings season got into full swing, the pan-European STOXX 600 ended the session 0.2 percent lower, down from the one-month high it reached in the previous session, as investors focused on a mixed bag of company results.

France's Publicis shares tumbled 8.8 percent after an unexpected drop in second-quarter sales caused by underperformance at its U.S. healthcare communications business .

"While operating margin was significantly ahead of expectations, the focus will be on the weaker revenue numbers, especially as [U.S. advertising agency] Omnicom earlier this week also underperformed expectations," wrote Liberum analysts.

Publicis took British rival WPP down nearly 3 percent along with it, and the media sector fell 1.4 percent.

"Investors will weigh lower-than-expected licence growth and muted underlying margin expansion against continued momentum in cloud," said Goldman Sachs analysts.

Basic resources stocks dragged, down 1.6 percent and near a three-month low, as metals prices resumed their selloff after a brief respite.

Overall, investors are optimistic going into the European earnings season, which is expected to deliver stronger growth than the first quarter.

"Earnings globally are still coming in on average higher than expectations," said Christopher Peel, chief investment officer at Tavistock Wealth. "I don't see anything going to stop it unless the trade tariff spat escalates and starts to bite."

Topping the STOXX was French telecoms firm Iliad, up 7.4 percent on news the company had reached 1 million subscribers in Italy and would extend its low-cost offer.